An investor in Houston-based Buckeye Partners has sued to halt a planned vote on a proposed $6.5 billion deal to sell the the petroleum distributor to an Australian investment management firm, claiming that the firm’s brass failed to disclose key financial information and possible conflicts among its directors.

The proposed class action, filed on June 28 in the U.S. District Court for the Southern District of New York, argued that investors needed more information to decide whether to support the transaction at a scheduled special meeting of the company’s limited partners on July 31.